Modern computer networks typically communicate using discrete packets or frames of data according to predefined protocols. There are multiple such standards, including the ubiquitous TCP and IP standards. For all but the simplest local topologies, networks employ intermediate nodes between the end-devices. Bridges, switches, and/or routers, are all examples of intermediate nodes.
As used herein, a network switch is any intermediate device that forwards packets between end-devices and/or other intermediate devices. Switches operate at the data link layer (layer 2) and sometimes the network layer (layer 3) of the OSI Reference Model, and therefore typically support any packet protocol. A switch has a plurality of input and output ports. Although a typical switch has only 8, 16, or other relatively small number of ports, it is known to connect switches together to provide large numbers of inputs and outputs. Prior art FIG. 1 shows a typical arrangement of switch modules into a large switch that provides 128 inputs and 128 outputs.
One problem with simple embodiments of the prior art design of FIG. 1 is that failure of any given switch destroys integrity of the entire switching system. One solution is to provide entire redundant backup systems (external redundancy), so that a spare system can quickly replace functionality of a defective system. That solution, however, is overly expensive because an entire backup must be deployed for each working system. The solution is also problematic in that the redundant system must be engaged upon failure of substantially any component within the working system. Another solution is to provide redundant modules within the system, and to deploy those modules intelligently (internal redundancy). But that solution is problematic because all the components are situated locally to one another. A fire, earthquake or other catastrophe will still terminally disrupt the functionality of the entire system.
U.S. Pat. No. 6,256,546 to Beshai (March 2002) describes a protocol that uses an adaptive packet header to simplify packet routing and increase transfer speed among switch modules. Beshai's system is advantageous because it is not limited to a fixed cell length, such as the 53 byte length of an Asynchronous Transfer Mode (ATM) system, and because it reportedly has better quality of service and higher throughput that an Internetworking Protocol (IP) switched network. The Beshai patent, is incorporated herein by reference along with all other extrinsic material discussed herein
Prior art FIG. 1A depicts a system according to Beshai's '546 patent. There, pluralities of edge modules (ingress modules 110A-D and egress modules 130A-D) are interconnected by a passive core 120. Each of the ingress modules 110A-D accept data packets in multiple formats, adds a standardized header that indicates a destination for the packet, and switches the packets to the appropriate egress modules 130A-D through the passive core 120. At the egress modules 130A-D the header is removed from the packet, and the packet is transferred to a sink in its native format. The solid lines of 112A-112D depict unencapsulated information arriving to circuit ports, ATM ports, frame relay ports, IP ports, and UTM ports. Similarly, the solid lines of 132A-D depict unencapsulated information exiting to the various ports in the native format of the information. The dotted lines of core 120 and facing portions of the ingress 110A-D and egress 130A-D modules depict information that is contained UTM headed packets. The entire system 100 operates as a single distributed switch, in which all switching is done at the edge (ingress and egress modules).
Despite numerous potential advantages, Beshai's solution in the '546 patent has significant drawbacks. First, although the system is described as a multi-service switch (with circuit ports, ATM ports, frame relay ports, IP ports, and UTM ports), there is no contemplation of using the switch as an Ethernet switch. Ethernet offers significant advantages over other protocols, including connectionless stateful communication. A second drawback is that the optical core is contemplated to be entirely passive. The routes need to be set up and torn down before packets are switched across the core. As such Beshai does not propose a distributed switching fabric, he only discloses a distributed edge fabric with optical cross-connected cores. A third, related disadvantage, is that Beshai's concept only supports a single channel from one module to another. All of those deficiencies reduce functionality.
Beshai publication no. 2001/0006522 (Jul. 2001) resolves one of the deficiencies of the '546 patent, namely the single channel limitation between modules. In the '522 application Beshai teaches a switching system having packet-switching edge modules and channel switching core modules. As shown in prior art FIG. 1B, traffic entering the system through ports 162A is sorted at each edge module 160A-D, and switched to various core elements 180A-C via paths 170. The core elements switch the traffic to other destination edge modules 180A-C, for delivery to final destinations. Beshai contemplates that the core elements can use channel switching to minimize the potential wasted time in a pure TDM (time division mode) system, and that the entire system can use time counter co-ordination to realize harmonious reconfiguration of edge modules and core modules.
Leaving aside the switching mechanisms between and within the core elements, the channel switching core of the '522 application provides nothing more than virtual channels between edge devices. It does not switch individual packets of data. Thus, even though the '522 application incorporates by reference Beshai's Ser. No. 09/244824 application regarding High-Capacity Packet Switch (issued as U.S. Pat. No. 6,721,271 in April 2004), the '522 application still fails to teach, suggest, or motivate one of ordinary skill to provide a fully distributed network (edge and core) that acts as a single switch.
What is still needed is a switching system in which the switching takes place both at the distributed edge nodes and within a distributed core, and where the entire system acts as a single switch.